Compliant porous materials have numerous applications in consumer products and in medicine. In automobiles, for example, random, open cell foams may be used as a cushioning material in seating, headrests, and armrests. Such foam may inhibit the flow of air more than is desired, compromising the comfort of the user, and the mass of such foam padding may be a factor in the design of the automobile.
In the medical industry, various materials are used for casts, wound care pads, padding, prostheses, bedding, and mobility devices. Ideally, such a material would allow the circulation of air through the material, and provide some measure of structural strength, so that it may be suitable for immobilizing a portion of the patient if used as a cast, or for supporting the patient's weight if used as bedding. In many of these applications, continuous contact with, or pressure on, the patient's skin may cause harm to the skin, such as bedsores, by affecting aeration of the skin and subcutaneous circulation. In such applications it is desired that the material used be permeable to air, and avoid forming regions of high pressure which may affect the patient's circulation.
Moreover, in health care applications it may be beneficial to apply a partial vacuum to the patient's skin to aid in wound healing or to accelerate the evaporation of surface moisture which otherwise may promote pathologies. It also may be beneficial for the health care provider to be able to adjust certain characteristics of the material, such as its stiffness and its permeability. The ability to adjust the stiffness, for example, may make it possible to adjust the immobilizing capacity of a cast until it is just adequate, so as to produce as little patient discomfort as possible.
A material with adjustable physical properties may also have applications in other fields, such as in making deployable structures for space. Like an inflatable structure, an adjustable stiffness material may be maintained stowed by a stowing restraint during launch and then after launch its stiffness may be increased allowing it to resume its original shape.
Thus, there is a need for a porous, permeable, compliant material, the physical properties of which may be adjusted after fabrication.